The following numbers are rough guidelines based on the numbers taken from the Quake 4 models. These numbers had been generated by importing different models and using the modelling software to list the amount of triangles.

1st Person Weapon Total: 2000 - 2800 Both Arms: 1300

Looking at UT3 I think "Perhaps this is a good solution when player see a only a weapon without hands, parts of body etc." (because it's easy for animation and modeling).

Shadow mesh is a greatly simplified version of your model. As name implies, it is used for shadow calculations. To make one, apply material named: textures/common/shadow or textures/common/shadow2 to your simplified model, and hide it within the complex model.

I never been heard about "shadow mesh". Perhaps you mean "collision model" (if viewmodel can collide with world)?But hands material in weapons.mtr includes "noshadows" and "noselfshadow". Is this is not enough?Thanks.

You are correct, hands/vwep's don't need a shadow mesh because they're just in the players view. It would be the 3rd person models. A mis-thinking on my part.